1. Field of the Invention
This invention relates to a collar attached to the side of a manhole to protect an outside drop adjacent the manhole.
2. Description of the Related Art
When an outside drop is used adjacent a manhole the outside drop is subject to damage and subsequent leaks by rocks and other fill material and due to shifting of the ground, the weight of the pipes and other factors. It is desired to have a protective collar around the drop pipe that will hold the pipes in place.
Currently protective collars are very heavy which makes them difficult and expensive to transport and install. The protective collars in use need to be set on a solid base as part of the base of the manhole, which makes the manhole itself heavier, more expensive, labor intensive and more difficult to install in the ground. The collars surrounding a drop pipe must be made the correct size to support the drop pipe, collars and connections, particularly at the top of the outside drop where there is a T connection and at the bottom of the outside drop where there is an elbow pipe connection. Since riser collars are made of concrete they are very heavy and require tools to lift the collar parts into place and in some cases cement mortared together. Since the riser collars are not fastened to the manhole they may have gaps between the manhole and the collar or may shift way from the manhole.
Outside drop pipes are generally made from ductile iron, which is heavy, expensive and hard to work with and are protected by a concrete collar. Plastic pipe is lighter, costs less, is easier to connect and easier to work with. However plastic pipe is more subject to damage and needs protection.
Prior plastic collars for outside drops on manholes, such as applicant's prior patent U.S. Pat. No. 6,695,002, required assembly of two halves of the collar at the job site and several collar sections for the height of the drop. The outside drop pipes can be of several different diameters, which require different sized collars. It is desired to have a one-piece collar of one diameter for any size outside drop pipe.